MIPS: smp: Warn on too early irq enable

Just to catch a potential issue.
Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: Sergei Shtylyov <sshtylyov@mvista.com>
Cc: David Daney <david.daney@cavium.com>
Acked-by: David Daney <david.daney@cavium.com>
Patchwork: https://patchwork.linux-mips.org/patch/3852/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/smp.c

@@ -130,6 +130,11 @@ asmlinkage __cpuinit void start_secondary(void)
 
 	synchronise_count_slave();
 
+	/*
+	 * irq will be enabled in ->smp_finish(), enabling it too early
+	 * is dangerous.
+	 */
+	WARN_ON_ONCE(!irqs_disabled());
 	mp_ops->smp_finish();
 
 	cpu_idle();